A magnet produced by cast iron, nickel, and the alloy of iron is called artificial magnet. The magnets which are used in the laboratories are artificial magnets. Their characteristic is this that they are of regular shape. In industries and scientific works, artificial magnets are used. Their magnetism is very strong. An electromagnet is one of such magnets.
Materials which have high permeability, low feeble magnetization intensity and a small area of hysteresis loop are ideal materials for good electromagnets. That means, soft and energy dissipations in hysteresis cycle are less in these magnets. An electromagnet is a type of magnet in which the magnetic field is produced by an electric current.
In soft (cast) iron, the above properties exist and hence it is used for making good electromagnets. Some alloys e.g. permalloy (alloy of iron and nickel) and stalloy (Fe+ 4% silicon) have high magnetic permeability’s and hence are used for making electromagnets.
In a U-shaped cast iron insulated wires are wrapped and if a current is allowed to flow through the wise then an electromagnet is produced. When the current flow stops, magnetism disappears. A magnetic field of a current carrying solenoid (Figure) behaves like the magnetic field of a bar magnet. If a piece of iron is inserted inside a solenoid its magnetism increases. During the flow of current, it becomes a very strong magnet. It is called electromagnet. The magnetic field of this magnet can be increased in the following ways –
(1) by increasing the current flow
(2) by increasing the number of turns in the solenoid.